Trying to figure out if it's worth it

That's the normal preformance parameters of that type motor stock, just broken in, well tuned & running properly.

It's a common misconception that shift kits aid top speed - they don't, if anything they (very) marginally reduce absolute top speed through increased friction & drag (additional chains, redirects & bearings)... provided the final ratio is the same between geared & ungeared comparison ofc.

What they do provide (at the cost of somewhat increased complexity & thus maintenance) is vastly improved acceleration & a more comfortable cruise, as you can gear it so you're not running redline at your desired speed.

The single most desirable aftermarket part for a distinct increase in preformance is nothing more than an expansion chamber exhaust - it's an intrinsic part of a two stroke engine, left out of the kits to cut costs & can be had for as little as $20 from ebay/etc (some fabrication required as those are pit bike/scooter pipes). The most important preformance modification is "port matching" - opening the intake & exhaust manifolds (grind/file) & trimming the intake & exhaust gaskets to match the intake & exhaust ports in the engine as best you're able - which is far easier than it sounds lol http://motorbicycling.com/showpost.php?p=164391&postcount=25 & http://motorbicycling.com/showpost.php?p=164403&postcount=27 from this thread: http://motorbicycling.com/showthread.php?t=16646

2strokes and aluminum frames are not a good mix

unless you make custom mounts the 2stroke kits will not fit due to the odd tubes the frame uses.

Even mounting a friction drive to this bicycle is a tricky job due to how the frame is made

Being that it is a full suspenion bicycle you would need a custom chain tensioner and the Sick bike Parts shiftkit mount will not fit this Bicycle due to the tubes used to make the frame. The stock Vbrakes are stamped POS and need to be replaced with better brakes

Yes traveling at redline/WOT will shorten the life of the motor 4strokes are built much better

I do own a avalon so yes I do know the short coming of that Bicycle
http://motorbicycling.com/showthread.php?t=38406

A lot of places claim "150MPG" or "up to 150MPG" on those kits, but that's not realistic, from my experience.

I've had 5 66cc kits and they've all averaged 80-90MPG. Granted, I'm 6'4" 230 or so in tennis shoes, but I also pedal a lot under 30.

If you want that engine to last at 30-35MPH, you need a tall gear (36T or less) and the ability to pedal up to 10MPH or so before you let the clutch out.

Yes- a 36 or less REALLY cuts down on the revs in that range- since you are lightweight, if you arent riding very steep hills or mountains you'll have no problems- a 36 would take you up almost anything anyway-

I have a 34- a $30 investment that easily gets a 30 cruise, and the motor is starting to scream at 35, so I haven't pushed beyond, because
http://www.ebay.com/itm/34-T-Sprocket-Bicycle-Engine-Kit-Motorized-Bike-/120936669817

it IS a VERY PRACTICAL: hobby if you keep that approach in mind- I spent a couple of years finding out how I liked the bike- the bigger gear, 700c rolling wheels, bilet intake, perpendicular alloy handlebars, even a lighter better rolling 415 Trike chain- sound dampeners and a longer pipe

you can always go to a shift kit later, but try the basics first- build the "Chinese Junk" of motor transport

now I don't want to mess with it all that much- arthritis and tension- but I just save all kinds of miles and gas expense on the car. Happy Boating!